[PATCH 04/12] perf jitdump: Prevent integer underflow in debug info size calculation

[Arnaldo Carvalho de Melo]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

jit_repipe_debug_info() and jit_repipe_unwinding_info() compute payload
sizes by subtracting the fixed header size from total_size:

  sz = jr->prefix.total_size - sizeof(jr->info);

When total_size is smaller than the header struct (from a truncated or
corrupted jitdump record), the subtraction underflows to a massive
value, causing an oversized allocation followed by an OOB memcpy.

Validate that total_size covers at least the fixed header before the
subtraction in both functions.

Fixes: 598b7c6919c7 ("perf jit: add source line info support")
Fixes: 0284fecd13b6 ("perf jit: Add unwinding support")
Reported-by: sashiko-bot <sashiko-bot@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Stefano Sanfilippo <ssanfilippo@xxxxxxxxxxxx>
Assisted-by: Claude:claude-opus-4.6
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/jitdump.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index 14bd23c8d1963e92..f79e9420c6bd7c51 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -671,6 +671,10 @@ static int jit_repipe_debug_info(struct jit_buf_desc *jd, union jr_entry *jr)
 	if (!(jd && jr))
 		return -1;
 
+	/* total_size must cover at least the fixed header */
+	if (jr->prefix.total_size < sizeof(jr->info))
+		return -1;
+
 	sz  = jr->prefix.total_size - sizeof(jr->info);
 	data = malloc(sz);
 	if (!data)
@@ -699,6 +703,10 @@ jit_repipe_unwinding_info(struct jit_buf_desc *jd, union jr_entry *jr)
 	if (!(jd && jr))
 		return -1;
 
+	/* total_size must cover at least the fixed header */
+	if (jr->prefix.total_size < sizeof(jr->unwinding))
+		return -1;
+
 	unwinding_data_size  = jr->prefix.total_size - sizeof(jr->unwinding);
 	unwinding_data = malloc(unwinding_data_size);
 	if (!unwinding_data)
-- 
2.55.0